In recent years, electric vehicles, hybrid vehicles, etc. in which an electricity storage device, such as a battery, a capacitor, etc., and an inverter, and a motor driven by the inverter are mounted as motive power sources, are drawing attention as environment-friendly motor vehicles.
A hybrid vehicle equipped with an external charging function of charging the battery through the use of an external electric power source is known. According to the hybrid vehicle equipped with the external charging function, if the battery can be charged, for example, from the household commercial electric power source, various merits will be achieved, including improved fuel economy, reduced frequency of going to petrol stations for refueling, etc.
Japanese Patent Application Publication No. JP-A-8-154307 discloses such an external charging function-equipped hybrid vehicle. This hybrid vehicle includes a battery chargeable by an external charger, an electric motor that drives wheels by electric power from the battery, the control means for controlling the working of the electric motor, an internal combustion engine that is directly or indirectly used to drive the vehicle, and traveling time-related amount calculation means for calculating an amount related to the traveling time after the battery has been charged by the external charger. The control means restricts the output of the electric motor if the traveling time-related amount calculated by the traveling time-related amount calculation means reaches a predetermined amount.
In this hybrid vehicle, if the vehicle travels for a long time without external charging, the output of the electric motor is restricted. If inevitably the travel is continued while the internal combustion engine consumes fuel, the output of the electric motor is restricted, so that the driver is urged to perform the external charging. Therefore, according to this hybrid vehicle, the degree of dependence on the internal combustion engine can be reduced.
A hybrid vehicle disclosed in Japanese Patent Application Publication No. JP-A-8-154307 is a vehicle that reduces the degree of dependence on the internal combustion engine, that is, a vehicle that actively uses the electric power (commercial electric power) supplied from an external electric power source (generally, a commercial electric power source) as a power source. However, in the generation of commercial electric power, a large amount of carbon dioxide is generated in the fire power generation in which electric power is generated by burning petroleum, a gas, etc. Therefore, for true contribution to environmental protection, there is a need for considering the generating process of electric power as well.
In order to cope with fluctuations in the demand for electric power depending on the season and the time of day, or the like, the power generation by electric power companies is carried out by a plurality of electric power generation methods such as the fire power generation, the atomic power generation, the hydraulic power generation, etc. The emission amount of carbon dioxide per unit electric power varies depending on the electric power generation methods. As stated above, the emission amount of carbon dioxide is particularly large in the fire power generation. Therefore, in an electric vehicle equipped with an external charging function that is capable of charging the battery from a commercial electric power source, if merely the amount of charging from the commercial electric power source is increased, there is a possibility of insufficient contribution to environmental protection.